From the manual:
Circuit Diagram (Power Supply area).
: Covers TX from 1.8–54 MHz (amateur bands) and RX from 30 kHz–56 MHz. Power Requirements yaesu ft-891 service manual
: Accessing the internal alignment menu (e.g., for reference frequency or meter calibration) requires specific key combinations detailed in the Technical Supplement Repair Warning From the manual: Circuit Diagram (Power Supply area)
The is a technical document intended for use by qualified technicians to maintain, calibrate, and repair the transceiver. While the Operating Manual covers day-to-day use, the service manual provides the deep architectural details needed for troubleshooting. Technical Overview yaesu ft-891 service manual